A group of players--whether it is 2 or 200--who are fully isolated from the rest of the network is what we call an island. Islands are pretty rare and mostly are counterfactuals like the one we're talking about here. Even when a low-level league, perhaps a USAPL league, starts up in a remote area where Fargo Ratings are not so entrenched, there is usually at least SOME coupling. So if you start a league in a retirement community in Kalispel MT with 40 players, many brand new, it's going to be at a low level generally. But there is probably going to be one player who winters in Arizona and plays in a league there and another who has 30 games from play in Billings and another who played half a season and moved away to be near his kids in Minnesota. You've forgotten about him, but he is playing at a VFW in MN and that is adjusting the whole Kalispel community. We would then call that a weakly coupled group.
In general, the higher the level of play for a group, the more connected it will be. So you can bet that if we have a group from somewhere in Oregon that seems unconnected or weakly connected to the rest of the world, it's a low level of play. Identifying these islands is not so easy. They are [jargon alert] related to small and zero eigenvalues of the information matrix.
When people say what is the average rating of the whole group, it depends strongly on how we cull the group. Below is the 40,000 players who have play in the last two years and also have a total of between 100 and 300 games in the system. The average is around 430.
If we look at the average of players entered in a tournament we get a very different number
If we look at the average established rating, very different number
Average of players with 500+ games in the system, very different number
View attachment 739565